Knowledgebase
How to add a swap file
Posted by Mike C. on 03 January 2010 09:49 PM
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Q. I need additional swap space to improve my system performance. How do I add a swap file to Linux system? A. In Linux, as in most other Unix-like operating systems, it is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast[7] as swap partitions, although Red Hat recommends using a swap partition. The administrative flexibility of swap files outweighs that of partitions; since modern high capacity hard drives can remap physical sectors, no partition is guaranteed to be contiguous. You can add swap file as a dedicated partition or use following instructions to create a swap file. Procedure to add a swap file You need to use dd command to create swapfile. Next you need to use mkswap command to set up a Linux swap area on a device or in a file. a) Login as the root user b) Type following command to create 512MB swap file (1024 * 512MB = 524288 block size): # dd if=/dev/zero of=/swapfile1 bs=1024 count=524288 c) Set up a Linux swap area: # mkswap /swapfile1 d) Activate /swapfile1 swap space immediately: # swapon /swapfile1 e) To activate /swapfile1 after Linux system reboot, add entry to /etc/fstab file. Open this file using text editor such as vi: # vi /etc/fstab Append following line: /swapfile1 swap swap defaults 0 0 So next time Linux comes up after reboot, it enables the new swap file for you automatically. g) How do I verify swap is activated or not? Simply use free command: $ free -m | |
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